On Tue, Sep 14, 2021 at 7:38 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > Hello, > > This is the 11th version of the series to fix the stacktrace with kretprobe on x86. > > The previous version is here; > > https://lore.kernel.org/all/162756755600.301564.4957591913842010341.stgit@devnote2/ > > This version is rebased on the latest tip/master branch and includes the kprobe cleanup > series[1][2]. No code change. > > [1] https://lore.kernel.org/bpf/162748615977.59465.13262421617578791515.stgit@devnote2/ > [2] https://lore.kernel.org/linux-csky/20210727133426.2919710-1-punitagrawal@xxxxxxxxx/ > > > With this series, unwinder can unwind stack correctly from ftrace as below; > > # cd /sys/kernel/debug/tracing > # echo > trace > # echo 1 > options/sym-offset > # echo r vfs_read >> kprobe_events > # echo r full_proxy_read >> kprobe_events > # echo traceoff:1 > events/kprobes/r_vfs_read_0/trigger > # echo stacktrace:1 > events/kprobes/r_full_proxy_read_0/trigger > # echo 1 > events/kprobes/enable > # cat /sys/kernel/debug/kprobes/list > ffffffff813bedf0 r full_proxy_read+0x0 [FTRACE] > ffffffff812c13e0 r vfs_read+0x0 [FTRACE] > # echo 0 > events/kprobes/enable > # cat trace > # tracer: nop > # > # entries-in-buffer/entries-written: 3/3 #P:8 > # > # _-----=> irqs-off > # / _----=> need-resched > # | / _---=> hardirq/softirq > # || / _--=> preempt-depth > # ||| / _-=> migrate-disable > # |||| / delay > # TASK-PID CPU# ||||| TIMESTAMP FUNCTION > # | | | ||||| | | > cat-136 [000] ...1. 14.474966: r_full_proxy_read_0: (vfs_read+0x99/0x190 <- full_proxy_read) > cat-136 [000] ...1. 14.474970: <stack trace> > => kretprobe_trace_func+0x209/0x300 > => kretprobe_dispatcher+0x9d/0xb0 > => __kretprobe_trampoline_handler+0xd4/0x1b0 > => trampoline_handler+0x43/0x60 > => __kretprobe_trampoline+0x2a/0x50 > => vfs_read+0x99/0x190 > => ksys_read+0x68/0xe0 > => do_syscall_64+0x3b/0x90 > => entry_SYSCALL_64_after_hwframe+0x44/0xae > cat-136 [000] ...1. 14.474971: r_vfs_read_0: (ksys_read+0x68/0xe0 <- vfs_read) > > This shows the double return probes (vfs_read() and full_proxy_read()) on the stack > correctly unwinded. (vfs_read() returns to 'ksys_read+0x68' and full_proxy_read() > returns to 'vfs_read+0x99') > > This also changes the kretprobe behavisor a bit, now the instraction pointer in > the 'pt_regs' passed to kretprobe user handler is correctly set the real return > address. So user handlers can get it via instruction_pointer() API, and can use > stack_trace_save_regs(). > > You can also get this series from > git://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/kretprobe-stackfix-v11 > > > Thank you, > > --- > > Josh Poimboeuf (3): > objtool: Add frame-pointer-specific function ignore > objtool: Ignore unwind hints for ignored functions > x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline() > > Masami Hiramatsu (19): > kprobes: treewide: Cleanup the error messages for kprobes > kprobes: Fix coding style issues > kprobes: Use IS_ENABLED() instead of kprobes_built_in() > kprobes: Add assertions for required lock > kprobes: treewide: Use 'kprobe_opcode_t *' for the code address in get_optimized_kprobe() > kprobes: Use bool type for functions which returns boolean value > ia64: kprobes: Fix to pass correct trampoline address to the handler > kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor() > kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() > kprobes: treewide: Make it harder to refer kretprobe_trampoline directly > kprobes: Add kretprobe_find_ret_addr() for searching return address > ARC: Add instruction_pointer_set() API > ia64: Add instruction_pointer_set() API > arm: kprobes: Make space for instruction pointer on stack > kprobes: Enable stacktrace from pt_regs in kretprobe handler > x86/kprobes: Push a fake return address at kretprobe_trampoline > x86/unwind: Recover kretprobe trampoline entry > tracing: Show kretprobe unknown indicator only for kretprobe_trampoline > x86/kprobes: Fixup return address in generic trampoline handler > > Punit Agrawal (5): > kprobes: Do not use local variable when creating debugfs file > kprobes: Use helper to parse boolean input from userspace > kprobe: Simplify prepare_kprobe() by dropping redundant version > csky: ftrace: Drop duplicate implementation of arch_check_ftrace_location() > kprobes: Make arch_check_ftrace_location static > Re-tested with latest BPF selftests and retsnoop tool utilizing kretprobe and capturing stack traces (broken without these changes). Looks good, thank you! Tested-by: Andrii Nakryiko <andriin@xxxxxxxxxx> > > arch/arc/include/asm/kprobes.h | 2 > arch/arc/include/asm/ptrace.h | 5 > arch/arc/kernel/kprobes.c | 13 - > arch/arm/probes/kprobes/core.c | 15 - > arch/arm/probes/kprobes/opt-arm.c | 7 > arch/arm64/include/asm/kprobes.h | 2 > arch/arm64/kernel/probes/kprobes.c | 10 > arch/arm64/kernel/probes/kprobes_trampoline.S | 4 > arch/csky/include/asm/kprobes.h | 2 > arch/csky/kernel/probes/ftrace.c | 7 > arch/csky/kernel/probes/kprobes.c | 14 - > arch/csky/kernel/probes/kprobes_trampoline.S | 4 > arch/ia64/include/asm/ptrace.h | 5 > arch/ia64/kernel/kprobes.c | 15 - > arch/mips/kernel/kprobes.c | 26 + > arch/parisc/kernel/kprobes.c | 6 > arch/powerpc/include/asm/kprobes.h | 2 > arch/powerpc/kernel/kprobes.c | 29 - > arch/powerpc/kernel/optprobes.c | 8 > arch/powerpc/kernel/stacktrace.c | 2 > arch/riscv/include/asm/kprobes.h | 2 > arch/riscv/kernel/probes/kprobes.c | 15 - > arch/riscv/kernel/probes/kprobes_trampoline.S | 4 > arch/s390/include/asm/kprobes.h | 2 > arch/s390/kernel/kprobes.c | 16 - > arch/s390/kernel/stacktrace.c | 2 > arch/sh/include/asm/kprobes.h | 2 > arch/sh/kernel/kprobes.c | 12 - > arch/sparc/include/asm/kprobes.h | 2 > arch/sparc/kernel/kprobes.c | 12 - > arch/x86/include/asm/kprobes.h | 1 > arch/x86/include/asm/unwind.h | 23 + > arch/x86/include/asm/unwind_hints.h | 5 > arch/x86/kernel/kprobes/core.c | 71 +++- > arch/x86/kernel/kprobes/opt.c | 6 > arch/x86/kernel/unwind_frame.c | 3 > arch/x86/kernel/unwind_guess.c | 3 > arch/x86/kernel/unwind_orc.c | 21 + > include/linux/kprobes.h | 113 ++++-- > include/linux/objtool.h | 12 + > kernel/kprobes.c | 502 ++++++++++++++----------- > kernel/trace/trace_kprobe.c | 2 > kernel/trace/trace_output.c | 17 - > lib/error-inject.c | 3 > tools/include/linux/objtool.h | 12 + > tools/objtool/check.c | 2 > 46 files changed, 607 insertions(+), 436 deletions(-) > > -- > Masami Hiramatsu (Linaro) <mhiramat@xxxxxxxxxx>
